Hi Miguel Z,
The resource below explains how to get your video files onto your iPhone:
iTunes: Frequently asked questions about viewing and syncing videos - Apple Support
https://support.apple.com/en-us/HT201784
Can I sync my own video through iTunes?
Yes, as long as the video file is in a format that iTunes can re-encode. Add the file to your iTunes library and then create versions optimized for your device using the File > Create New Version menu.
What video content works with mobile devices?
Video content purchased from the iTunes Store.
Video files after using the iTunes File > Create New Version > Create iPod or iPhone version option.
iTunes Store Movie Rentals (Requires iTunes 9 or later).
Does the video need to be encoded in a special way?
All mobile devices which iTunes can sync video to can play the following video formats:
H.264
File formats: .m4v, .mp4, and .mov
Video: Up to 768 kbits/sec, 320 x 240, 30 frames per second (fps), Baseline Profile up to Level 1.3.
Audio: AAC-LC up to 160 kbits/sec, 48 Khz, and stereo audio.
MPEG-4
File formats: .m4v, .mp4, and .mov
Video: Up to 2.5 Mbits/sec, 480 x 480, 30 fps, Simple Profile.
Audio: AAC-LC up to 160 kbits/sec, 48 Khz, stereo audio.
Take care,
- Judy